Filter having impedance matching circuits

ABSTRACT

A filter package is provided with a support structure, a filter device having terminals, impedance matching circuits formed on the support structure and electrically connected to at least some of the terminals of the filter device, and at least one electrical ground structure electrically connected to the impedance matching circuits. Moreover, the filter package has an outer housing to contain the support structure, filter device impedance matching circuits, and at least one ground structure.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority to U.S. patentapplication Ser. No. 13/007,708 filed on Jan. 17, 2011, published as US2011/0109403 A1, which is a continuation of U.S. patent application Ser.No. 11/985,812 filed Nov. 16, 2007, issued as U.S. Pat. No. 8,060,156,which claims the benefit under 35 U.S.C. §119(e) of U.S. ProvisionalApplication No. 60/866,118 filed Nov. 16, 2006, and U.S. ProvisionalApplication No. 60/867,272 filed Nov. 27, 2006, which are all herebyincorporated by reference.

TECHNICAL FIELD

The invention relates generally to a filter for use in a wirelesscommunications device.

BACKGROUND

Wireless communications devices, such as wireless terminals or wirelessbase stations, include wireless transceivers to perform wirelesscommunications, such as radio frequency (RF) communications. A wirelesstransceiver commonly includes one or more filters, such as a band passfilter, a band reject filter, or other types of filters. A band rejectfilter is used to reject or attenuate signals having frequencies withina particular band, while allowing frequencies outside the band to passthrough. A band pass filter, on the other hand, allows frequencieswithin a band to pass through, while rejecting or attenuating signalshaving frequencies outside the band. Other types of filters include lowpass filters, high pass filters, and so forth.

Certain types of high performance filters use external impedancematching circuits that are connected to terminals of the filter. An“external” matching circuit refers to a matching circuit that is locatedoutside a package of the filter. An issue associated with using externalmatching circuits is that impedances associated with electricalconnecting structures between electronic circuitry inside the filterpackage and the external matching circuits can limit effectiveness ofthe filter at higher frequencies. Therefore, many conventional filtersmay not be effectively used in high-frequency wireless communicationsdevices. Moreover, due to issues associated with external matchingcircuits, some high performance filters may simply omit the use ofmatching circuits for some terminals of the filters, which can come atthe expense of reduced filter performance.

SUMMARY

In general, a filter package has an outer housing, a support structure,and a filter device having plural terminals. Matching circuits formed onthe support structure are electrically connected to at least some of theplural terminals of the filter device. The matching circuits areelectrically connected to at least one electrical ground structure. Thesupport structure, filter device, matching circuits, and at least oneground structure are contained in the outer housing.

Other or alternative features will become apparent from the followingdescription, from the drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view of a substrate assembly for use in afilter package with internal matching circuits, according to anembodiment.

FIG. 1B is a bottom view of the substrate assembly of FIG. 1A.

FIGS. 2 and 3 are cross-sectional views of different embodiments of afilter package.

FIGS. 4A-4B, 5A-5B, 6, and 7 illustrate other embodiments of substrateassemblies used in filter packages.

FIG. 8 is a cross-sectional view of a multi-layer substrate assembly,according to another embodiment.

FIG. 9 is a schematic view of a filter package on a circuit board,according to an embodiment.

FIG. 10 is a block diagram of an example arrangement including a mobilestation and a base station in a wireless communications network, whereat least one of the mobile station and base station can include a filterpackage according to some embodiments.

DETAILED DESCRIPTION

In the following description, numerous details are set forth to providean understanding of some embodiments. However, it will be understood bythose skilled in the art that some embodiments may be practiced withoutthese details and that numerous variations or modifications from thedescribed embodiments may be possible.

In accordance with some embodiments, a filter package includes an outerhousing containing a filter device and internal impedance matchingcircuits that are electrically connected to the filter device. Thefilter device can be a “high frequency” filter device in some exampleimplementations. A “high-frequency” filter device is able to operate atrelatively high frequencies, such as in the gigahertz (GHz) range. Asexamples, such high-frequency filter devices include surface acousticwave (SAW) filter devices, bulk acoustic wave (BAW) filter devices, andother types of filter devices. In some examples, the filter devices aredesigned to be band rejection filter devices, in which signals havingfrequencies within a band of frequencies are rejected (or attenuated),whereas signals having frequencies outside the band of frequencies areaccepted (or allowed to pass through the filter device). Another type offilter device is a band pass filter device, in which signals havingfrequencies within the band are allowed to pass through the filterdevice, whereas signals having frequencies outside the band are rejected(or attenuated). In other implementations, other types of filter devicescan be employed, such as low pass filter devices, high pass filterdevices, and so forth.

The filter package can be used in a wireless communications device or insome other type of electronic device.

In accordance with some embodiments, internal impedance matchingcircuits contained within the outer housing of a filter package providefor higher quality impedance matching and allow for more effectiveoperations at high frequencies (e.g., in the GHz range such as 1 GHz orgreater). The internal impedance matching circuits can be in the form ofmatching transmission lines or discrete matching components. Thematching circuits are electrically connected to at least one groundstructure within the filter package outer housing. By providing internalmatching circuits that can be connected to an internal ground structure,external matching components (located outside the filter package outerhousing) can be avoided or reduced. Providing internal matching circuitsallows for electrical connection structures between the inside of thefilter package and external matching components to be omitted orreduced, which is beneficial since such electrical connection structurestend to introduce discontinuity, as well as parasitic and resistivelosses that may adversely affect filter device performance at higherfrequencies. For example, resistances introduced by such electricalconnection structures can cause unacceptable passband loss. Also, byproviding matching circuits internally within the filter package andavoiding or reducing external matching components, the footprint takenup by the filter package and associated circuitry can be reduced toprovide for more efficient usage of space of a circuit board on whichthe filter package is to be mounted. Also, by reducing the number ofexternal matching components that have to be electrically coupled to thefilter device, manufacturing yield of circuit boards can be improved (byreducing the number of components on the circuit board) and testrepeatability (as well as performance) can be improved. This can lead toenhanced efficiencies during mass production or manufacture.

FIG. 1A is a perspective view of a substrate assembly that can beprovided within a filter package according to an embodiment. Thesubstrate assembly depicted in FIG. 1A include a substrate carrier 110(or other type of support structure) on which is mounted a filter device102. In the embodiment of FIG. 1A, the bottom surface of the filterdevice 102 is mounted on an upper surface of the substrate carrier 110.In different embodiments, other forms of attachment between the filterdevice 102 and the substrate carrier 110 can be provided, as discussedfurther below.

An upper surface 104 of the filter device 102 provides various contactterminals (where each contact terminal is formed of an electricallyconductive material) that are electrically connected to internal nodesof the filter device 102. In an alternative implementation, the contactterminals can be provided on other parts of the filter device 102. Twoof the contact terminals provided on the upper surface 104 of the filterdevice 102 are an input terminal and an output terminal that areelectrically connected by bond wires 126 and 128, respectively, to aninput transmission line 112 and an output transmission line 114,respectively. The input transmission line 112 is electrically connectedto receive an input signal from outside the filter package, and theoutput transmission line 114 is to provide an output signal (afterfiltering applied by the filter device 102 on the input signal) to theoutside of the filter package. In the embodiment of FIG. 1A, thetransmission lines 112 and 114 can be much shorter and closer to bondwires 126 and 128 to further minimize resistive losses. In a typicalimplementation, the filter package is mounted on a circuit board. Theinput and output signals are signals provided over conductive traces ofthe circuit board.

The upper surface 104 of the filter device 102 also has other contactterminals that are electrically connected by bond wires 122 tocorresponding matching transmission lines 106, and by bond wires 124 tocorresponding matching transmission lines 107. In the depictedembodiment, the matching transmission lines 106 and 107 are provided onthe upper surface of the substrate carrier 110 (as are the input andoutput transmission lines 112, 114). Typically these matchingtransmission lines are relatively short, to provide relatively smallvalues of inductance, and to provide a relatively high quality factor(e.g., low resistive loss can be important for reducing pass bandlosses). The matching transmission lines 106, 107 can be any one ofmicrostrip lines (where a microstrip line is a conducting stripseparated from a ground plane by a dielectric layer), striplines (wherea stripline is a conducting strip sandwiched between two parallel groundplanes separated from the conducting strip by dielectric), coplanarwaveguide lines (a conductor separated by a pair of coplanar groundlines), or other types of transmission lines.

As discussed further below, the transmission lines 106, 107 can also (oralternatively) be provided on the bottom surface of the substratecarrier 110 in other implementations. As yet another alternative, thesubstrate carrier 110 can be omitted with the transmission lines formedon an inner surface of the filter package outer housing. Alternatively,instead of using matching transmission lines, discrete components can beused instead to provide impedance matching. Examples of impedancematching discrete components include resistors, capacitors, andinductors. More generally, the matching transmission lines and/ormatching discrete components are referred to as “matching circuits,”which are generally circuits (either in the form of transmission linesor in the form of discrete components, or both) that are used to provideimpedance matching. The matching circuits provide relatively smallhigh-Q matching inductances that are useful for reducing pass band loss.

Although not depicted in FIG. 1A, note that at least some of thematching transmission lines 106, 107 can also be electrically connectedto discrete matching components, if desired.

As further depicted in FIG. 1A, a ground plane 108 is provided on theupper surface of the substrate carrier 110, with the ground plane 108having openings to receive the transmission lines 106, 107 and the inputand output transmission lines 112, 114. Note that gaps are providedbetween sides of the transmission lines 106, 107, 112, 114, and theground plane 108. To electrically connect the matching transmissionlines 106, 107 to the ground plane 108, bond wires 130 (one set of bondwires 130 is labeled 130A) and 131 (one set of bond wires 131 is labeled131A) can be used. Shunting the transmission lines 106, 107 to groundusing the bond wires 130, 131 of FIG. 1A allows for provision of high-Qinductors.

The bond wires 130 electrically connect the matching transmission lines106 to the ground plane 108, whereas the bond wires 131 electricallyconnect the transmission lines 107 to the ground plane 108. As depictedin FIG. 1A, each matching transmission line 106, 107 is electricallyconnected by a corresponding pair of bond wires to the ground plane 108.In different implementations, each transmission line 106, 107 can beelectrically connected by just one bond wire to the ground plane 108, oralternatively, by more than two bond wires to the ground plane 108.

The connection point of a set of one or more bond wires to a matchingtransmission line 106 or 107 can be varied to achieve a desiredelectrical length of the transmission line. By moving the connectionpoint of the set of one or more bond wires to the matching transmissionline 106 or 107 further away from the filter device 102, a longerelectrical length of the transmission line is provided. On the otherhand, by moving the connection point of the set of one or more bondwires to the matching transmission line closer to the filter device, ashorter length of the transmission line is provided. Effectively, byvarying the electrical length of the matching transmission line, theamount of inductance that is electrically connected to a correspondingcontact terminal of the filter device is varied. Each transmission line106 or 107 can be considered a shunt stub that is tunable to a specificelectrical length by shorting the transmission line to ground at adesired location of the transmission line. In the example of FIG. 1A,note that the connection point of the pair of bond wires 130A to thecorresponding matching transmission line 106 is closer to the filterdevice 102 than the connection point of the pair of bond wires 131A tothe corresponding transmission line 107. Therefore, the electricallength of the transmission line 106 connected to bond wires 130A isshorter than the electrical length of the transmission line 107connected to bond wires 131A. Note that in the example of FIG. 1A, theelectrical lengths of the transmission lines 106, 107 correspond tophysical lengths shorter than the physical lengths of the transmissionlines 106, 107, due to locations of the connection points of the bondwires 130, 131 away from the ends of the transmission lines.

During manufacturing of the filter package, the locations of theconnection points of the bond wires to different matching transmissionlines can be tuned according to the impedance matching needs of thedifferent contact terminals of the filter device 102. Such tuning canprovide more effective matching circuits to improve performance of thefilter package. By using internal matching circuits according to someembodiments, filter performance can be optimized for various internalnodes of the filter device. The impedance matching for the contactterminals of the filter device can be performed inside the filterpackage, close to the filter device, such that a smaller resistive lossand less inherent parasitic are associated with the matching circuitsand filter package. Moreover, the impedance matching can be performedwith high accuracy and high repeatability since the electrical lengthsof matching transmission lines can be tuned for different contactterminals of the filter device.

The ground plane 108 and the transmission lines 106, 107 can be formedon the upper surface of the substrate carrier 110 by depositing anelectrically conductive layer on the upper surface of the substratecarrier 110 and etching the deposited electrically conductive layer toprovide the ground plane 108, transmission lines 106, 107, andtransmission lines 112, 114. In other implementations, other techniquesof forming the ground plane 108 and transmission lines 106, 107, 112,and 114 can be used.

Note that the substrate carrier 110 can be formed of a dielectricmaterial (that is electrically insulating), such as ceramic or the like.

FIG. 1B shows the bottom view of the substrate carrier 110 of FIG. 1A,where the bottom view has a ground plane 116 with cutouts 117A and 117Bto allow for an input contact pad 118 and an output contact pad 120provided on the bottom surface of the substrate carrier 110. The inputcontact pad 118 and the output contact pad 120 are electricallyconnected to electrically conductive structures (depicted in FIGS. 2 and3 and discussed below) to allow for the input and output pads 118, 120to receive and transmit input and output signals, respectively. Thesmall circles in FIG. 1B represent vias to interconnect the inputcontact pad 118, the output contact pad 120, and the ground plane 116,to the input transmission line 112, output transmission line 114, andground plane 108, respectively.

The ground plane 116 and the input and output contact pads 118, 120 canbe formed by depositing an electrically conductive layer on the lowersurface of the substrate carrier 110, and then etching the depositedelectrically conductive layer to form the ground plane 116 and input andoutput contact pads 118, 120.

FIG. 2 shows the substrate assembly depicted in FIGS. 1A-1B provided ina chamber 200 defined by an outer housing of the filter package. Theouter housing includes side walls 202, a bottom segment 204, and a topcap 206 (or other covering structure). The outer housing can be formedof an electrically insulating material such as ceramic or the like.During manufacture of the filter package, the substrate assembly thatincludes the substrate carrier 110 and the filter device 102 is firstprovided into the chamber 200 of the outer housing. The input and outputcontact pads 118, 120 on the bottom surface of the substrate carrier 110are electrically connected to package interconnect structures 210 and212, respectively, which extend through the lower segment 204 of theouter housing to electrically connect to external pads 214, 216,respectively. The package interconnect structures can include vias(vertical interconnect structures) and an internal metal layer(horizontal interconnect structure). Note that the base 208 provided bythe bottom segment 204 can provide connection pads corresponding to thecontact pads 118, 120 of the substrate carrier 110. The external pads214, 216 are electrically contacted to external electrically structures,such as electrical structures provided on a circuit board. The groundplane 116 can be attached to the housing base ground area with solderreflow or conductive epoxy or the like. The input contact pad 118 andthe output contact pad 120 can also be attached to housing base padswhich are connected to the external pads 214 and 216.

Once the substrate assembly is positioned on a base 208 provided in thechamber 200 of the outer housing, and the electrical connection has beenmade between the input and output pads 118, 120 and the packageinterconnect structures 210, 212, the top cap 206 can be attached to theside walls 202 of the outer housing. The top cap 206 can be adhesivelyattached, or attached by some other attachment or bonding mechanism, tothe side walls 202 of the outer housing. Once assembled, as depicted inFIG. 2, the outer housing and the substrate assembly including thesubstrate carrier 110 and filter device 102 form the filter packagedepicted in FIG. 2. Note that the substrate assembly is completelyenclosed by the outer housing made up of the top cap 206, side walls202, and lower segment 204.

FIG. 3 shows a slightly different embodiment of the filter package. Thefilter package of FIG. 3 uses a different mounting mechanism between thesubstrate assembly and the base 208 of the lower segment 204 of theouter housing. In FIG. 3, the mounting mechanism is in the form of metalor solder bumps 240 that are electrically connected to packageinterconnect structures 210, 212 (FIG. 2). In the FIG. 3 embodiment, amatching transmission line 250 is depicted as being provided on thebottom side of the substrate carrier 110. Providing matchingtransmission line(s) on both sides of the substrate carrier 110 allowsfor miniaturization or reduction in size of the substrate assembly sothat the filter package can be made even smaller.

As noted above, the substrate carrier 110 can be omitted in otherimplementations, with the filter device 102 provided directly on thebase 208 of the outer housing of the filter package. In such animplementation, the matching transmission lines (similar to 106, 107)can be formed on the base 208.

In a variant of the embodiments discussed above, the input and outputtransmission lines 112 and 114 can be electrically connected by bondwires to leadframe pads of the package. Also, it is possible that theground plane 108 can be connected by bond wires to ground leadframe padsof the package.

FIGS. 4A and 4B show a variation of the substrate assembly depicted inFIGS. 1A-1B, where common reference numerals are used to identify commonelements. In FIGS. 4A and 4B, a cavity 300 is provided in or through thesubstrate carrier 110A, such that the filter device 102 can fit insidethe cavity 300. The cavity 300 can extend all the way through thesubstrate carrier 110A, or alternatively, the cavity 300 can be a recessthat does not extend all the way through the substrate carrier 110A. Byproviding the cavity 300, the filter device is at least slightlyembedded inside the substrate carrier 110 such that the upper surface104 of the filter device 102 is closer to the upper surface of thesubstrate carrier 110A. This can reduce the length of the bond wires122, 124, 126, 128 used to electrically connect the contact terminals ofthe filter device 102 to the corresponding transmission lines 106, 107,112, 114 on the substrate carrier 110A. Reducing the length of the bondwires allows for reduced inductances, which may improve high-frequencyperformance of the filter device 102.

FIGS. 5A-5B illustrate a variation of the embodiment of FIGS. 4A-4B. InFIGS. 5A-5B, instead of using bond wires 130, 131 to electricallyconnect matching transmission lines 106, 107 to the ground plane 108,the FIG. 5A embodiment instead directly connects an end portion ofmatching transmission lines 400, 401 to the ground plane 108. Asdepicted in FIG. 5A, end portions 402 of corresponding matchingtransmission lines 400 are electrically contacted to the ground plane108. Similarly, end portions 404 of corresponding matching transmissionlines 401 are electrically contacted to the ground plane 108. Thelengths of the matching transmission lines 400, 401 can be varied duringthe manufacturing process of the substrate assembly depicted in FIG. 5Ato provide different electrical lengths for matching inductanceselectrically connected to corresponding contact terminals of the filterdevice 102. Note that in this embodiment, the electrical lengths of thetransmission lines 400,401 are proportional to the physical lengths ofthe transmission lines 400, 401.

The benefit of using the FIGS. 5A-5B embodiment is that bond wires 130,131 do not have to be used, which can improve manufacturing yield.

FIG. 6 is a top view of a substrate assembly including a substratecarrier 501 according to another embodiment. In FIG. 6, matchingtransmission lines 500 are provided for connection to correspondingcontact terminals on the upper surface of the filter device 102. Bondwires electrically connecting the matching transmission lines 500 to thefilter device 102 and to the ground plane 108 are not depicted forpurposes of clarity. In addition, FIG. 6 shows that input and outputtransmission lines 502 and 504 are further electrically connected todiscrete components that are used for impedance matching for thetransmission lines 502, 504. In the example of FIG. 6, the inputtransmission line 502 is electrically connected to matching discretecomponents 506 and 507, which are both interconnected between thetransmission line 502 and the ground plane 508. Similarly, the outputtransmission line 504 is electrically connected to matching discretecomponents 508, 509, which are both interconnected between thetransmission line 504 and the ground plane 108. The discrete componentscan be implemented with one or more devices, such as capacitors,resistors, inductors, and so forth. Note that input transmission line502 and output transmission line 504 may also optionally each include anintermediate discrete component between matching discrete components 506and 507 or between matching discrete components 508 and 509.

Vias 510 and 512 are provided on corresponding transmission lines 502and 504 to allow for the transmission lines 502, 504 to be electricallyconnected to input and output contact pads on the other side of thesubstrate carrier 501. Note that the bottom side of the substratecarrier 501 can have structures similar to that depicted in FIG. 1B inone implementation.

Although not depicted in FIG. 6, note that at least some of the matchingtransmission lines 500 can also be electrically connected to discretematching components, if desired.

FIG. 7 shows the bottom view of a carrier structure 501 according toanother embodiment. Note that the structures depicted in the bottom viewof FIG. 7 can be used in conjunction with the structures in the top viewof FIG. 6, or alternatively, can be used with a different arrangement onthe upper surface of the substrate carrier (such as in an arrangementwhere matching transmission lines 500 are omitted).

The bottom view depicted in FIG. 7 shows that matching transmissionlines 520 can also be provided on the bottom surface of the substratecarrier 501. These matching transmission lines 520 are electricallyconnected by vias 522 to corresponding electrical structures 524 (FIG.6) on the upper surface (FIG. 6) of the substrate carrier 501.

FIG. 8 shows a cross-sectional view of a substrate assembly according toanother embodiment. In the example of FIG. 8, two dielectric layers 550and 552 are provided, with an electrically conductive layer 554 providedon the top surface, an electrically conductive layer 558 providedbetween the dielectric layers, and an electrically conductive layer 556provided on the bottom surface. To electrically connect conductivestructures on the upper layer 554 and the bottom layer 558, vias 560 canbe used. The upper and lower conductive layers 554, 556, as well as theintermediate electrically conductive layer 558, can be used to implementtransmission lines and/or ground planes.

FIG. 9 shows an example filter package 600 provided on a circuit board602. As depicted in FIG. 9, a substrate carrier 110 with the filterdevice 102 (e.g., in the form of an acoustic or microelectromechanicalsystems die) is provided inside the package 600.

The filter device 102 includes various internal components 604 (e.g.,resonators) and internal nodes 605 that are connected to contactterminals 606, 608, 610, 612, and 614. A pad or contact point 620 on thecircuit board 602 provides the input signal to the filter package 600,while a pad or contact point 622 on the circuit board 602 receives anoutput signal from the filter package 600. The pads or contact points620, 622 are electrically connected through respective packagetransitions 624, 626 (e.g., package terminals, castellations, pins,vias, electrodes, etc.) to the substrate carrier 110. In the embodimentof FIG. 9, matching circuits 628, 630 on the substrate carrier 110 areelectrically connected to corresponding contact terminals 606, 610 (suchas by bond wires) of the filter device 102. Typically, the contactterminals 606, 610 are input and output contact terminals for receivinginput signals and transmitting output signals, respectively.

In addition, the contact terminals 608, 612 of the filter device 102 areelectrically connected to matching transmission lines 632, 634,respectively, similar to the matching transmission lines describedabove. Each of the matching transmission lines 632, 634 are electricallyconnected, such as by bond wires or by other electrical connection, toground. Each of the transmission lines 632, 624 act as a matchinginductor to the shunt resonators.

In the example of FIG. 9, the remaining contact terminal 614 of thefilter device 102 is not electrically connected to a matchingtransmission line, but instead, is directly electrically connected tothe ground plane 108. More than one contact terminal 614 can be usedwhen multiple shunt resonators or internal components exist.

As further depicted in FIG. 9, the filter package 600 can further havepackage transitions 632, 634, 636 (e.g., package terminals,castellations, vias, pins, electrodes, etc.) that are electricallyconnected to external ground (ground of the circuit board 602). Theground plane(s) inside the filter package 600 is (are) electricallyconnected through these package transitions 632, 634, 636 to externalground.

FIG. 10 shows an example arrangement of a wireless communicationsnetwork that includes a mobile station 700 and a base station 702 thatare able to communicate wirelessly, such as using radio frequency (RF)signaling 704, with each other. In accordance with some embodiments, anyone of the filter packages can be provided in at least one of the mobilestation 700 and base station 702. As depicted in FIG. 10, a filterpackage 708 is provided in an RF transceiver 706 of the mobile station,while a filter package 714 is provided in an RF transceiver 712 of thebase station 702. The RF transceivers 706, 712 are electricallyconnected to processors 710, 716 in the respective mobile station 700and base station 702. The processor 710, RF transceiver 706, and filterpackage 708 can be provided on a common circuit board, such as thatdepicted in FIG. 9. Similarly, the processor 716, RF transceiver 712,and filter package 714 of the base station 702 can be provided on acommon circuit board.

Each of the mobile station 700 and base station 702 is an example of awireless communications device. In other applications, filter packagesaccording to some embodiments can be used in other types of electronicdevices.

In the foregoing description, numerous details are set forth to providean understanding of the present invention. However, it will beunderstood by those skilled in the art that the present invention may bepracticed without these details. While the invention has been disclosedwith respect to a limited number of embodiments, those skilled in theart will appreciate numerous modifications and variations therefrom. Itis intended that the appended claims cover such modifications andvariations as fall within the true spirit and scope of the invention.

What is claimed is:
 1. A filter, comprising: a support structure; afilter element having plural terminals; at least one electrical groundstructure, the electrical ground structure comprising a ground planesupported by the support structure, the ground plane having openings;impedance matching circuits electrically coupled between at least someof the plural terminals of the filter device and the ground plane, theimpedance matching circuits comprising impedance matching linessupported by the support structure in the openings in the ground planeso that that impedance matching lines and the ground plane aresubstantially in a common plane; and an outer housing containing thesupport structure, the filter element, the impedance matching circuits,and the at least one electrical ground structure.
 2. The filter of claim1, wherein the support structure comprises a substrate carrier mountedon a base provided inside the outer housing, and wherein the impedancematching circuits are provided on the substrate carrier.
 3. The filterof claim 1, wherein the support structure comprises an internal surfaceof the outer housing, and wherein the impedance matching circuits areprovided on the internal surface of the outer housing.
 4. The filter ofclaim 1, further comprising: input and output transmission lines on thesupport structure to provide an input signal to, and output signal from,the filter device; and leadframe pads electrically connected to theinput and output transmission lines and to the electrical groundstructure.
 5. The filter of claim 1, wherein the impedance matchinglines are on a surface of the support structure and electrical lengthsof the impedance matching lines are tuned for corresponding ones of theat least some plural terminals.
 6. The filter of claim 5, wherein theimpedance matching lines comprise bond wires to ground, lengths of thebond wires being tuned for corresponding ones of the at least someplural terminals.
 7. The filter of claim 1, wherein at least one of theimpedance matching lines is connected to a discrete matching component.8. The filter of claim 7, wherein the discrete matching componentcomprises at least one of a capacitance and an inductance.
 9. The filterof claim 1, wherein at least one of the impedance matching circuitscomprises a transmission line formed on the support structure.
 10. Thefilter of claim 1, wherein the outer housing is mounted to at least oneof a substrate and a circuit board.
 11. A method of making a filter,comprising: providing a support structure; providing a filter elementhaving plural terminals; providing at least one electrical groundstructure, the electrical ground structure comprising a ground planesupported by the support structure, the ground plane having openings;providing impedance matching circuits electrically coupled between atleast some of the plural terminals of the filter device and the groundplane, the impedance matching circuits comprising impedance matchinglines supported by the support structure in the openings in the groundplane so that that impedance matching lines and the ground plane aresubstantially in a common plane; and providing an outer housingcontaining the support structure, the filter element, the impedancematching circuits, and the at least one electrical ground structure. 12.The method of claim 11, wherein the support structure comprises asubstrate carrier mounted on a base provided inside the outer housing,and wherein the impedance matching circuits are provided on thesubstrate carrier.
 13. The method of claim 11, wherein the supportstructure comprises an internal surface of the outer housing, andwherein the impedance matching circuits are provided on the internalsurface of the outer housing.
 14. The method of claim 11, furthercomprising: providing input and output transmission lines on the supportstructure to provide an input signal to, and output signal from, thefilter device; and electrically connecting leadframe pads to the inputand output transmission lines and to the electrical ground structure.15. The method of claim 11, wherein the impedance matching lines are ona surface of the support structure and electrical lengths of theimpedance matching lines are tuned for corresponding ones of the atleast some plural terminals.
 16. The method of claim 15, wherein theimpedance matching lines comprise bond wires to ground, comprisingtuning lengths of the bond wires for corresponding ones of the at leastsome plural terminals.
 17. The method of claim 11, wherein at least oneof the impedance matching lines is connected to a discrete matchingcomponent.
 18. The method of claim 11, wherein the discrete matchingcomponent comprises at least one of a capacitance and an inductance. 19.The method of claim 11, wherein at least one of the impedance matchingcircuits comprises a transmission line formed on the support structure.20. The method of claim 11, further comprising mounting the outerhousing to at least one of a substrate and a circuit board.